Valhalla 2 not even an option?! You guys are buying the Sennns 600, 650s and 6XX by the truck load. They sound the BEST when paired with a good OTL amp. I thought the 650s were mediocre cans until I paired them with the Valhalla 2. Now they are as good as every thinks they should be.

If y'all are gonna spend hundreds on cans like the Senns you need to look up impedance matching for amps.

You're half right. "Some" people don't have $250+ to spend on a dedicated amp after spending $200+ on a pair of fucking headphones. An amp is necessary, but not what you're suggesting which is "relatively" expensive and not necessary when all you need is enough voltage to be able to power them correctly. Also, sound signature is all about preference and a tube amp changes the nature of the headphone to where it might get too warm for the preference of others; stop being so brash.

Voltage isn't everything, you need current to actually move the drivers properly. A lot of people get hung up on getting these headphones running loud enough, but not enough attention paid to distortion. I'm also not disagreeing with you on budget concern. But if money wasn't an issue, it makes sense to also buy an amp that lets you drive HD6XX to the fullest. You can certainly do better than a O2 or Magni, and certainly better than a Valhalla too.

There's no point in buying good headphones and a bad amp. the whole chain of devices running from your source (may it be analog or digital) need to be up to par. garbage in - garbage out, the best sound you'll hear will be determined by your worst component. I predict a lot of frustration and a lot of bad reviews for the 6XX because of people not doing the research and just thinking that headphones are headphones and that they can just plug them into a phone like their 20$ in-ears.

If you can only afford the headphones- you cannot afford the headphones.

Remember that the HD650 are 400$ headphones, you can't expect the supporting accessories for a 400$ product to be 50$. That's something to think about BEFORE buying a 400$ headphone at 200$.